Effects of whey protein edible coating on bacterial, chemical and sensory characteristics of frozen common kilka (Clupeonellia delitula)

The objective of the current study was to investigate the effects of whey protein coating on the quality of common Kilka during frozen storage. For this study, common Kilka was coated with 20% whey protein concentration. Non-coated Kilka also was used as a control. Coated and non-coated samples were then stored at -18 °C for six months. Bacterial, chemical and sensory properties of the samples were determined in each month. Results showed that Coliform, Escherichia coli and Pseudomonas bacteria contaminations were negative until the end of storage period in the covered samples. Total bacterial counts and Staphylococcus bacteria count were lower in the test samples compared with the control samples. Humidity, protein, lipid, ash and calorie contents were higher in test samples as compared with the control samples, while peroxide value, free fatty acids, thiobarbitoric acid, TVN and pH were lower in test samples. Taste, odor, color, tissue and overall acceptability were studied in the test and control samples. These specifications had a better quality in test samples compared with the control ones. These factors showed a significant difference in the uncoated samples (control) (p<0.05). Significant decrease was observed in bacterial counts in the covered and control samples. According to the statistical analysis in sensory specifications, there was a significant difference between the covered samples and the control ones (p<0.05). According to the results of experiments and statistical analysis, the covered samples had a favorable quality until the end of storage period but the control samples had lost their quality after three months

Chemical, microbiological and sensory evaluation of gutted kilka coated with whey protein based edible film incorporated with sodium alginate during frozen storage

The effects of whey protein (12%) and sodium alginate (0.5%) on chemical, microbial and sensory changes and shelf life in kilka during frozen storage are investigated for up to 6 months. Total bacteria count and Staphylococcus bacteria counts(2 / 51 and 1 / 44 log CFU/g) in coated samples showed decrease in comparison with control samples(3.21- 2.28 log CFU/g). Moisture of coated samples had significant increase than control treatment (p<0.05). Protein, lipid, ash and calorie were higher in test samples as compared with the control samples. Free fatty acids, TBRS, peroxide value, TVN and pH in coated samples showed significant decrease in comparison with control (p<0.05). Sensory evaluation of coated samples showed significant difference in comparison with control (p<0.05). It is suggested that whey protein edible coating incorporated with sodium alginate can enhance quality and increase shelf life of kilka fish in storage of freezing up to 6 months

Disrupting the Acyl Carrier Protein/SpoT Interaction In Vivo: Identification of ACP Residues Involved in the Interaction and Consequence on Growth

In bacteria, Acyl Carrier Protein (ACP) is the central cofactor for fatty acid biosynthesis. It carries the acyl chain in elongation and must therefore interact successively with all the enzymes of this pathway. Yet, ACP also interacts with proteins of diverse unrelated function. Among them, the interaction with SpoT has been proposed to be involved in regulating ppGpp levels in the cell in response to fatty acid synthesis inhibition. In order to better understand this mechanism, we screened for ACP mutants unable to interact with SpoT in vivo by bacterial two-hybrid, but still functional for fatty acid synthesis. The position of the selected mutations indicated that the helix II of ACP is responsible for the interaction with SpoT. This suggested a mechanism of recognition similar to one used for the enzymes of fatty acid synthesis. Consistently, the interactions tested by bacterial two-hybrid of ACP with fatty acid synthesis enzymes were also affected by the mutations that prevented the interaction with SpoT. Yet, interestingly, the corresponding mutant strains were viable, and the phenotypes of one mutant suggested a defect in growth regulation

COMPARISON OF MEAT QUALITY OF FARMED ACIPENSER PERSICUS USING TWO PROCESSING METHODS OF DRY AND MIX SALTING

The processing and comparison of quality of meat in farmed Acipenser persicus using two methods of dry and mix salting was carried out to provide a new formula for processing new sturgeon products. Ten fish specimens with a mean weight and length of 2 kilograms and 60cmthat were farmed for two years were used in this study. The meat of the specimens was processed using pure salt and a mixture of salt and one percent madder. Two replicates were used for each method. In the first method, dry sodium chloride was used at a rate of 250g of sodium chloride per kilogram body weight of fish (dry salting). In the second method, about 109 of madder was added to the 250g of sodium chloride (mix salting). Microbial examinations included total bacterial counts, Staphylococcus and Coli form bacteria assessment and chemical examinations included salt, protein and fat absorption, TVN, peroxide, and pH tests. Sensory tests as well as microbial and chemical experiments were carried out for the quality control of the processed samples for a period of three months. According to the results, Iranian National Standard and pure plate culture method (10-1,10-2 and 10-3) Coliform counts in the two different meat samples was lower than 10 per gram of meat. The total bacterial count and the Staphylococcus bacteria count was higher in the meat samples processed with dry salting. Besides, the rate of salt absorption and peroxide was lower in these samples. The protein, fat, pH and humidity were higher in the samples treated with dry salting. However, taste, flavor and color of the meat processed with a mixture of sodium chloride and madder was higher quality than that processed with dry sodium chloride. No significant differences were observed in chemical factors such as TVN and salt absorption for the two processing methods. This was also the case for microbial analysis including bacterial counts such as Staphylococcus and total bacterial count

Putrescine and spermidine control degradation and synthesis of ornithine decarboxylase in Neurospora crassa.

Neurospora crassa mycelia, when starved for polyamines, have 50-70-fold more ornithine decarboxylase activity and enzyme protein than unstarved mycelia. Using isotopic labeling and immunoprecipitation, we determined the half-life and the synthetic rate of the enzyme in mycelia differing in the rates of synthesis of putrescine, the product of ornithine decarboxylase, and spermidine, the main end-product of the polyamine pathway. When the pathway was blocked between putrescine and spermidine, ornithine decarboxylase synthesis rose 4-5-fold, regardless of the accumulation of putrescine. This indicates that spermidine is a specific signal for the repression of enzyme synthesis. When both putrescine and spermidine synthesis were reduced, the half-life of the enzyme rapidly increased 10-fold. The presence of either putrescine or spermidine restored the normal enzyme half-life of 55 min. Tests for an ornithine decarboxylase inhibitory protein ("antizyme") were negative. The regulatory mechanisms activated by putrescine and spermidine account for most or all of the regulatory amplitude of this enzyme in N. crassa

Ornithine decarboxylase from Neurospora crassa. Purification, characterization, and regulation by inactivation.

Ornithine decarboxylase, a highly regulated enzyme of the polyamine pathway, was purified 670-fold from mycelia of Neurospora crassa that were highly augmented for enzyme activity. The enzyme is significantly different from those reported from three other lower eucaryotic organisms: Saccharomyces cerevisiae, Physarum polycephalum, and Tetrahymena pyriformis. Instead, the enzyme closely resembles the enzymes from mammals. The Mr = 110,000 enzyme is a dimer of 53,000 Da subunits, with a specific activity of 2,610 mumol per h per mg of protein. Antisera were raised to the purified enzyme and were rendered highly specific by cross-absorption with extracts of a mutant strain lacking ornithine decarboxylase protein. With the antisera, we show that the inactivation of the enzyme in response to polyamines is proportional to the loss of ornithine decarboxylase protein over almost 2 orders of magnitude. This is similar to the inactivation process in certain mammalian tissues, and different from the process in S. cerevisiae and P. polycephalum, in which enzyme modification, without proportional loss of antigen, accompanies enzyme inactivation. The N. crassa enzyme is therefore suitable as a microbial model for studies of the molecular regulation of the mammalian enzyme

Putrescine and spermidine control degradation and synthesis of ornithine decarboxylase in Neurospora crassa.

Neurospora crassa mycelia, when starved for polyamines, have 50-70-fold more ornithine decarboxylase activity and enzyme protein than unstarved mycelia. Using isotopic labeling and immunoprecipitation, we determined the half-life and the synthetic rate of the enzyme in mycelia differing in the rates of synthesis of putrescine, the product of ornithine decarboxylase, and spermidine, the main end-product of the polyamine pathway. When the pathway was blocked between putrescine and spermidine, ornithine decarboxylase synthesis rose 4-5-fold, regardless of the accumulation of putrescine. This indicates that spermidine is a specific signal for the repression of enzyme synthesis. When both putrescine and spermidine synthesis were reduced, the half-life of the enzyme rapidly increased 10-fold. The presence of either putrescine or spermidine restored the normal enzyme half-life of 55 min. Tests for an ornithine decarboxylase inhibitory protein ("antizyme") were negative. The regulatory mechanisms activated by putrescine and spermidine account for most or all of the regulatory amplitude of this enzyme in N. crassa